Such a device is known from German published specification No. P 3408554.8 (U.S. Pat. No. 4,671,104, and U.S. Pat. No. 4,691,559, English Pat. No. 2155639, Japanese published specification No. 75655/84). According to U.S. Pat. No. 4,691,559 FIG. 1 thereof, a test body 67 is provided from which a first bar device emerges vertically upwardly and merges into a second horizontal bar device 37. Here, the geometric central axis 21 is important. The second bar device 37 is mounted on a bearing device in the form of the rotor of a rotary magnet device 31. The disadvantages of this arrangement are as follows:
(a) There is friction in the bearing of the rotary magnet.
(b) It is true that the second bar device 37 is comparatively long, although by virtue of problems with mass and the problem of usefulness as a hand-held appliance soon applies limits to the length; nevertheless, upon a rotation as indicated by the arrow 39, the direction of the first bar device changes in relation to the geometric longitudinal axis 21, so that that side of the test body 67 which is closer to the rotary magnet 31 is pressed in that direction. However, the first bar device ought to remain in the geometric central axis 21 or only undergo a parallel translatory displacement, and then only by an amount which can be disregarded from the point of view of measurement technique.
(c) Measurement of hardness can be described as a method which derives results from finding out how a material behaves when subject to the action of force. By reason of the aforesaid properties, however, it is not with the prior art device possible to this degree to record the depth profile of the hardness. The hardness is particularly of interest right in the vicinity of the surface and to this end, the prior art device is not sensitive enough.
Devices of the relevant prior art include the following features:
A first bar device having an end portion and a geometric central axis.
A test body supported on the end portion, the geometric central axis of the first bar device passing through the middle of the test body.
A bearing device.
And, a second bar device substantially perpendicular to the first bar device, having one end portion rigidly connected to the first bar device and another end portion fixed in the longitudinal direction of the second bar device in such a way as to be immovable on the bearing device, the bearing device being immovable in the longitudinal direction of the second bar device.